Mold for helical springs



June 29, 1943. R WARD 2,322,757

MOLD FOR HELICAL SPRINGS Original Filed July 23, 1941 RALPH f. WARDPatented June 29, 1943 UNITED STATES PATENT OFFICE Original applicationJuly 23, 1941, Serial No. 403,724. Divided and this application June 16,1942, Serial No. 447,280

3 Claims.

This application is a division of my co-pending application, Serial No.403,724 for Mold for hellcal springs.

This invention relates to the spring-making art. and, more particularly,to the art of forming springs, by molding and subsequently curingorganic thermoplastic materials, in accordance with the processdescribed and claimed in my co-pending application Serial No. 403,768.

In one method of making springs according to the invention disclosed inmy co-pending application, Serial No. 403,768, a molded or extruded rodor bar is softened, as by heat, then shaped to a desired spring form,and then immersed in boiling water until it becomes resilient. Thismethod is particularly useful in the manufacture of helical extensionsprings which must have end loops, and the object of the inventiondescribed and claimed in this application is to provide a mold or formin which an extension spring may be made by the described process.

Other objects and features of novelty of the invention will be madeapparent by the following description and the annexed drawing, it beingunderstood, however, that such description and drawing are onlyillustrative of the invention and partly in elevation, of a moldaccording to my invention;

Fig. 2 is a sectional view taken on line 2-4 of Fig. 1, and

Fig. 3 is a sectional view taken on line 3-3 of Fig. 1.

In the drawing there is illustrated a mold apparatus intendedparticularly for the formation of extension springs from molded orextruded rods or bars of organic thermoplastic material in accordancewith the process described and claimed in my aforesaid co-pendingapplication, Serial No. 403,768. In this apparatus, an inner cylindricalform 2 is provided having at each end a form for the end loop which isnecessary in extension springs. Each such loop form comprises a recess 4formed in the outer wall of the cylindrical'form and spaced from theadjacent end thereof, from which a groove in the outer wall passes tothe end of the form and is curved over the end, as at 6, and then awayfrom the end and also circumferentially, as at 8, being then ofdecreasing depth until its bottom merges with the outer wall of theform.

In the use of this apparatus to form an extension spring one end of arod or bar ill of organic thermoplastic material which has beensoftened, as by being passed through water heated to or F., is insertedaxially into one of the recesses 4, the adjacent material of the rod orbar being then brought over the end of the form through the groove 6 toprovide one end loop, the rod being then coiled about the entire lengthof the form and the other end of the rod being passed over the end ofthe form in the groove 6 and anchored in the adjacent recess 4, thusproviding the second end loop. The form, with the coiled thermoplasticrod thereon, is then inserted into the outer mold-part II, the innerdiameter of which is of such a size as to tightly fit the outerperiphery of the coiled rod, after which the assembly is subjected tothe hot immersion step of my invention. The form 2 may then be removedfrom the outer mold-part and the helix, which is now resilient andspring-like, removed therefrom.

While I have described and illustrated but one form of my invention itwill be recognized by those skilled in the art that modification thereofmay be made and further embodiments discovered, all without departing inany way from the spirit or scope of the invention, for the limits ofwhich reference must be had to the appended claims.

What is claimed is:

1. A mold for a helical extension spring comprising a hollow cylindricalmold-part, a second cylindrical .mold-part disposed concentricallywithin the outer mold-part and being of such cross-sectional size thatan annular space is provided between the two mold-parts which is ofsufficient radial extent to receive a helix wound about the innermold-part and the outer face of which abuts the inner wall of the outermoldpart, the inner mold-part having means formed at at least one endthereof to receive an end of the helix and shaped to form such end as aloop.

2. A mold for a helical extension spring comprising a hollow cylindricalmold-part, a second cylindrical mold-part disposed concentrically withinthe outer mold-part and being of such cross-sectional size that anannular space is provided between the two mold-parts which is ofsuflicient radial extent to receive a helix wound about the innermold-part and the outer face of which abuts the inner wall of the outermoldpart, the inner mold-part having substantially longitudinallyextending grooves formed in the ends thereof within which the ends ofthe helix are received for the formation of loops on the ends oi thehelix.

3. A mold for a helical extension spring comprising a hollow cylindricalmold-part, a second cylindrical mold-part adapted to be disposedconcentrically within the outer mold-part and being of suchcross-sectional size that an annular space is provided between the twomold-parts when in such assembled condition, at least one end portion ofthe second mold-part having a recess in the wall thereof spaced from theend

